Such a fastening system for a rifle with a replaceable barrel known as such has been disclosed in the patent specification FI-20040200. It has been stated that it is possible to load a rifle by accident, for example, with a .22 LR caliber cartridge, although the rifle has a barrel for a .17 HMR (Hornady Magnum Rifle) cartridge, the diameter of which is approximately 1 mm smaller than the diameter of the barrel for the .22 LR cartridges. Test shots have been fired using a .22 LR cartridge in a rifle having the barrel for a .17 HMR cartridge and it has been noted that a lead bullet will compress so much that it will pass through the barrel, and does not cause any danger.